Skin Diseases That Cause Dark Spots. 1  Melasma: Itâs one of the commonest causes of grayish patches on the face. It mostly affects the forehead, cheeks, or the area between your mouth and nose. 2  Riehlâs Melanosis: It causes grayish or brownish patches on your face resulting from hyper-pigmentation.
In biology, tissue is a cellular organizational level intermediate between cells and a complete organ.A tissue is an ensemble of similar cells from the same origin that together carry out a specific function. Organs are then formed by the functional grouping together of multiple tissues.The study of tissue is known as histology or, in connection with disease, histopathology.unctions of epithelial tissue: 1  the cells of the body surface form the outer layer of skin. 2  inside the body, epithelial cells form the lining of the mouth & alimentary canal & protect these organs. 3  epithelial tissues help in absorption of water & nutrients.
Medical Definition of TISSUE. : an aggregate of cells usually of a particular kind together with their intercellular substance that form one of the structural materials of a plant or an animal and that in animals include connective tissue, epithelium, muscle tissue, and nerve tissue.ull Definition of TISSUE. 1. a: a fine lightweight often sheer fabric. 2. : a piece of soft absorbent tissue paper used especially as a handkerchief or for removing cosmetics.